package cn.cloud.all.security.web.header.writers;

import cn.cloud.all.security.web.header.HeaderWriter;
import org.springframework.util.Assert;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Provides support for <a href="https://wicg.github.io/feature-policy/">Feature
 * Policy</a>.
 * <p>
 * Feature Policy allows web developers to selectively enable, disable, and modify the
 * behavior of certain APIs and web features in the browser.
 * <p>
 * A declaration of a feature policy contains a set of security policy directives, each
 * responsible for declaring the restrictions for a particular feature type.
 *
 * @author Vedran Pavic
 * @author Ankur Pathak
 * @since 5.1
 */
public final class FeaturePolicyHeaderWriter implements HeaderWriter {

    private static final String FEATURE_POLICY_HEADER = "Feature-Policy";

    private String policyDirectives;

    /**
     * Create a new instance of {@link FeaturePolicyHeaderWriter} with supplied security
     * policy directive(s).
     *
     * @param policyDirectives the security policy directive(s)
     * @throws IllegalArgumentException if policyDirectives is {@code null} or empty
     */
    public FeaturePolicyHeaderWriter(String policyDirectives) {
        setPolicyDirectives(policyDirectives);
    }

    @Override
    public void writeHeaders(HttpServletRequest request, HttpServletResponse response) {
        if (!response.containsHeader(FEATURE_POLICY_HEADER)) {
            response.setHeader(FEATURE_POLICY_HEADER, this.policyDirectives);
        }
    }

    /**
     * Set the security policy directive(s) to be used in the response header.
     *
     * @param policyDirectives the security policy directive(s)
     * @throws IllegalArgumentException if policyDirectives is {@code null} or empty
     */
    public void setPolicyDirectives(String policyDirectives) {
        Assert.hasLength(policyDirectives, "policyDirectives must not be null or empty");
        this.policyDirectives = policyDirectives;
    }

    @Override
    public String toString() {
        return getClass().getName() + " [policyDirectives=" + this.policyDirectives + "]";
    }

}
